Engineered Bamboo I-Joists

Abstract

Many bamboo species are well regarded for their strength and rapid renewability, although the nonuniformity of bamboo poles has impeded use in developed countries. Described herein are the results of a pilot effort to develop engineered bamboo I-joists for use in common low-rise construction applications. Solid section bamboo materials were used to fabricate I-beams; flanges consisted of single-strand bamboo material and webs consisted of bamboo OSB or three-ply material. Experimental results indicate that flexural strengths were limited to 5.2 ksi (36 MPa) by the failure of the flange finger joints; shear strengths were 2.1 ksi (14 MPa) for the bamboo OSB and 3.3 ksi (22 MPa) for the three-ply web material. The modulus of elasticity averaged 2,000 ksi (14 GPa), while the shear modulus was 250 ksi (1.7 GPa) for the bamboo OSB and 140 ksi (0.94 GPa) for the three-ply material. Design values are developed from the test results following a hybrid approach based on ASTM procedures for wood I-joists and whole bamboo poles.